Method of curing thermosetting resin composition, thermosetting resin composition, and prepreg, metal-clad laminate, resin sheet, printed-wiring board, and sealing material in which thermosetting resin composition is used

ABSTRACT

A method of curing a thermosetting resin composition according to the present invention includes mixing a thermosetting resin containing a benzoxazine compound and a curing accelerator containing a triazine thiol compound to prepare a thermosetting resin composition, and heating this thermosetting resin composition to be cured.

TECHNICAL FIELD

The present invention relates to a method of curing a thermosettingresin composition, a thermosetting resin composition, and a prepreg, ametal-clad laminate, a resin sheet, a printed-wiring board, and asealing material in which the thermosetting resin composition is used,and particularly relates to a method of curing a thermosetting resincomposition that is suitable for an insulating material for a prepreg, alaminate, a resin sheet, a printed-wiring board, and the like, and asealing material for sealing a semiconductor or the like.

BACKGROUND ART

Conventionally, various types of thermosetting resin compositions havebeen used for insulating materials for printed-wiring boards and thelike, and sealing materials for sealing semiconductors and the like.There is a demand for these thermosetting resin compositions to beexcellent in the performance of electrical properties, heat resistance,and flame-retardancy, along with an improvement in the performance ofvarious types of electronics and a diversification of applications.

In such a background, in order to improve properties of thethermosetting resin compositions, it has been proposed that abenzoxazine compound that has excellent electrical properties and heatresistance and is useful for provision of flame-retardancy is mixed intothe thermosetting resin compositions as a resin component (see PatentDocument 1, for example). It has been known that this benzoxazinecompound is cured along with ring-opening polymerization of an oxazinering in a process in which the thermosetting resin composition is hotmolded. However, the benzoxazine compound has a slower cure ratecompared to other thermosetting resins such as an epoxy resin and imideresin, and thus there is a problem in that if the benzoxazine compoundis used as the component of the thermosetting resin, the benzoxazinecompound is not sufficiently cured under hot molding conditions underwhich laminates or sealing materials are generally molded, and it isdifficult for a cured material to have high heat resistance and a highglass transition point.

Also, it is possible to increase the degree of cure of the benzoxazinecompound, improve the heat resistance of the cured material, andincrease the glass transition point of the cured material throughextending a molding time period or raising a molding temperature duringhot molding. However, in that case, productivity decreases andmanufacturing costs increase, and it is difficult to control resinfluidity and the like during molding, as a result of which moldingproperties may deteriorate. Thus, there is an issue in that the degreeof freedom of designing hot molding conditions decreases.

Also, it has been conventionally proposed that a benzoxazine compound ismixed along with a phosphorus-containing compound into a thermosettingresin such as an epoxy resin or imide resin to prepare the thermosettingresin composition in order to become halogen-free and flame-retardant.However, if the content of the benzoxazine compound is increased, thecure rate of the resin decreases, and thus there is a concern that theabove-described various issues may arise. On the other hand, if thecontent of the benzoxazine compound is reduced, there is an issue inthat the properties of the benzoxazine compound are deteriorated.

In view of this, a phenol compound is used as the resin component incombination with the benzoxazine compound in order to accelerate curingof the benzoxazine compound, but the fact is that undercuring of thebenzoxazine compound has not been sufficiently addressed.

CITATION LIST Patent Literature

Patent Document 1: JP 2008-274274A

SUMMARY OF INVENTION Technical Problem

The present invention has been made in view of the above-describedissues, and an object thereof is to provide a method of curing athermosetting resin composition that can improve the cure rate of aresin composition containing a benzoxazine compound, a thermosettingresin composition, and a prepreg, a metal-clad laminate, and a sealingmaterial in which the thermosetting resin composition is used.

Solution to Problem

In view of circumstances of the conventional techniques described above,as a result of the earnest study of an effective method for acceleratinga curing reaction of the benzoxazine compound through trial and error,the inventors found that the curing reaction of the benzoxazine compoundcould be significantly improved through using a specific compound as acuring accelerator, and could accomplish the present invention.

A method of curing a thermosetting resin composition according to thepresent invention includes mixing a thermosetting resin containing abenzoxazine compound and a curing accelerator containing a triazinethiol compound to prepare a thermosetting resin composition, and heatingthe thermosetting resin composition to be cured.

It is preferable that the thermosetting resin composition be heated to50° C. or more to be cured.

It is preferable that the triazine thiol compound include a compoundhaving three or more thiol groups in one molecule.

It is also preferable that the triazine thiol compound include acompound having a triazine ring and a thiol group directly bound to thetriazine ring.

It is also preferable that the triazine thiol compound include acompound having a triazine ring and three or more thiol groups directlybound to the triazine ring.

It is preferable that a percentage of the triazine thiol compound to theentirety of the thermosetting resin composition be within a range of 0.1to 30% by mass.

It is preferable that the curing accelerator further include imidazole.

It is preferable that the thermosetting resin further include an epoxyresin.

A thermosetting resin composition according to the present inventionincludes a thermosetting resin containing a benzoxazine compound and acuring accelerator containing a triazine thiol compound.

It is preferable that a gel time of the thermosetting resin compositionaccording to the present invention at 200° C. be 7 minutes or less.

A prepreg according to the present invention is obtained throughimpregnating a fiber base material with the thermosetting resincomposition, and semi-curing the thermosetting resin composition.

A metal-clad laminate according to the present invention is obtainedthrough laminating the prepreg with a metal foil, and hot-press moldingthe laminated prepreg.

A resin sheet according to the present invention is obtained throughapplying the thermosetting resin composition onto a carrier sheet.

A printed-wiring board according to the present invention includes aninsulating layer made of a cured material of the thermosetting resincomposition.

A sealing material according to the present invention is made of thethermosetting resin composition.

Advantageous Effects of Invention

According to a method of curing a thermosetting resin compositionaccording to the present invention, it is possible to improve the curerate of a benzoxazine compound through using a curing acceleratorcontaining a triazine thiol compound.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of the present invention will be described.

A method of curing a thermosetting resin composition according to thisembodiment includes mixing a thermosetting resin containing abenzoxazine compound and a curing accelerator containing a triazinethiol compound to prepare a thermosetting resin composition, and heatingthe thermosetting resin composition to be cured.

There is no particular limitation on the benzoxazine compound as long asthe benzoxazine compound has a benzoxazine ring in the molecule, andfrom the point of view of obtaining good reactivity and cross-linkdensity in the cured material, it is preferable that the benzoxazinecompound include a compound having two or more benzoxazine rings in onemolecule. Specific examples of the compound included in the benzoxazinecompound include: Fa-based benzoxazine compounds obtained through areaction between a bisphenol compound and an amine compound (forexample, aniline), such as a bisphenol A-based benzoxazine compound or abisphenol F-based benzoxazine compound; and a Pd-based benzoxazinecompound obtained through a reaction between a phenyldiamine compoundand a phenol compound, such as a diaminodiphenylmethane-basedbenzoxazine compound. Benzoxazine compounds that are available ascommercial products can be used. For example, a bisphenol F-basedbenzoxazine compound, which is an Fa-based benzoxazine compound, has astructure as represented by Formula (1) below.

The thermosetting resin includes the benzoxazine compound as anessential component, and may include a thermosetting compound other thanthe benzoxazine compound. There is no particular limitation on thethermosetting compound other than the benzoxazine compound as long as itdoes not inhibit the curing reaction of the benzoxazine compound, andexamples thereof include epoxy resins, phenol resins, cyanate resins,isocyanate resins, unsaturated imide resins, amino resins, unsaturatedpolyester resins, allyl resins, dicyclopentadiene resins, siliconeresins, melamine resins, and the like. Among these resins, epoxy resinsand phenol resins are preferable as examples of resins that exhibit agood curing reaction in combination with the benzoxazine compound. Thesethermosetting resins may be used alone or in combination. Note thatexamples of the thermosetting compound that is to be mixed into thethermosetting resin include a compound that functions as a so-calledcuring agent (cross-linking agent) for the benzoxazine compound andanother resin component that is used in combination as a base resin.

If the thermosetting resin includes the benzoxazine compound and anepoxy resin, there is no particular limitation on the epoxy compoundsthat can be used, and examples thereof include bisphenol type epoxyresins, novolac type epoxy resins, alicyclic epoxy resins, glycidylesters, glycidyl amines, heterocyclic epoxy resins, brominated epoxyresins, and the like. Examples of the bisphenol type epoxy resins aboveinclude bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol Sepoxy resins, and the like. Examples of the novolac type epoxy resinsabove include phenol novolac epoxy resins, cresol novolac epoxy resins,bisphenol A-novolac epoxy resins, dicyclopentadiene novolac epoxyresins, and the like. Examples of the alicyclic epoxy resins aboveinclude 3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate,1-epoxylethyl-3,4-epoxycyclohexane, and the like. Examples of theglycidyl esters above include phthalic acid diglycidyl ester,tetrahydrophthalic acid diglycidyl ester, dimer acid glycidyl ester, andthe like. Examples of the glycidyl amines above include tetraglycidyldiaminodiphenylmethane, triglycidyl P-aminophenol,N,N-diglycidylaniline, and the like. Examples of the heterocyclic epoxyresins above include 1,3-diglycidyl-5,5-dimethylhydatointriglycidylisocyanurate, and the like. Also, examples of the brominatedepoxy resins include tetrabromobisphenol A epoxy resins,tetrabromobisphenol F epoxy resins, brominated cresol novolac epoxyresins, brominated phenol novolac epoxy resins, and the like. Theseepoxy resins may be used alone or in combination.

There is no particular limitation on the triazine thiol compoundincluded in the curing accelerator as long as it is a compound having atriazine ring and a thiol group (—SH) in the molecule, and the triazinethiol compound preferably includes a compound having three or more thiolgroups in one molecule. In this case, it is possible to further increasethe cure rate of the benzoxazine compound.

Also, it is preferable that the triazine thiol compound include acompound in which a thiol group is directly bound to a triazine ring, orin other words, a compound having a triazine ring and a thiol groupdirectly bound to the triazine ring. In this case, it is possible tofurther increase the cure rate of the benzoxazine compound. It isconceivable that the reasons for this are as follows. The thiol grouphas small activation energy to generate active hydrogen, and thereforethe thiol group has an excellent effect of accelerating the ring-openingpolymerization of benzoxazine. Thus, if benzoxazine is opened, a phenolgroup generated from benzoxazine serves as an acid catalyst, furtheraccelerating the ring-opening polymerization of benzoxazine.

It is also preferable that the triazine thiol compound include acompound having a triazine ring and three or more thiol groups directlybound to the triazine ring.

Specific examples of the compound that can be included in the triazinethiol compound include 2,4,6-trimercapto-s-triazine, which isrepresented by Formula (2) below.

It is preferable that the percentage of the triazine thiol compound tothe entirety of the thermosetting resin composition be within a range of0.1 to 30% by mass. Note that if the thermosetting resin compositioncontains an inorganic material such as an inorganic filler, theinorganic material is excluded from “the entirety of the thermosettingresin composition”. Also, if the thermosetting resin compositioncontains solvent, the solvent is excluded from “the entirety of thethermosetting resin composition”. If the percentage of the triazinethiol compound is 0.1% by mass or more, it is possible to obtain a goodcuring acceleration effect of the benzoxazine compound. If thepercentage of the triazine thiol compound is 30% by mass or less, it ispossible to obtain a necessary and sufficient curing acceleration effectof the benzoxazine compound, and to prevent any deterioration in otherproperties (deterioration in electrical properties, increase in metalcorrosiveness, and the like), which may be caused by an excess amount ofthiol groups. The percentage of triazine thiol compound is furtherdesirably within a range of 0.5 to 15% by mass, and more optimallywithin a range of 1 to 10% by mass.

The curing accelerator may also include another compound for cureacceleration other than the triazine thiol compound. There is noparticular limitation on the another compound for cure acceleration aslong as it can accelerate the curing reaction of the benzoxazinecompound, and examples thereof include imidazole-based compounds,organic phosphine-based compounds, and tertiary amine-based compounds.These compounds may be used alone or in combination. Among thesecompounds, the imidazole-based compound is preferably mixed into thecuring accelerator. In this case, the cure rate of the benzoxazinecompound can be further increased by good synergistic effects resultingfrom the combination of the triazine thiol compound and theimidazole-based compound.

Specific examples of the imidazole-based compounds include2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole,1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole,2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole,1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole,1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole,1-cyanoethyl-2-phenylimidazole, and 1-aminomethyl-2-methylimidazole. Itis preferable that the percentage of the imidazole-based compound to theentirety of the thermosetting resin composition be within a range of 0.1to 1% by mass.

The thermosetting resin composition may further contain anothercomponent as required. Examples of the another component include aninorganic filler, a flame retardant, and an additive agent.

Known inorganic filler may be used to improve the heat resistance,flame-retardancy, and heat conductivity of a cured material of thethermosetting resin composition, and decrease the expansion coefficientthereof. Specific examples of the inorganic fillers include silica,alumina, talc, aluminum hydroxide, magnesium hydroxide, titanium oxide,mica, aluminum borate, barium sulfate, and calcium carbonate. Theseinorganic fillers may be used alone or in combination. Also, a surfacetreatment may be performed on the inorganic filler with an epoxy silanecoupling agent or an amino silane coupling agent, and alternatively sucha surface treatment may not be performed thereon.

Examples of the flame retardants include phosphorus-based flameretardants and halogen-based flame retardants. Specific examples of thephosphorus-based flame retardants include phosphate esters such ascondensed phosphate esters and cyclic phosphate esters; phosphazenecompounds such as cyclic phosphazene compounds; and phosphinate-basedflame retardants such as metal phosphinates like aluminumdialkylphosphinate. Also, examples of the halogen-based flame retardantsinclude bromine-based flame retardants. Also, from the point of view ofhalogen free, the phosphorus-based flame retardant is preferably used.The flame retardants that are described above as examples may be usedalone or in combination.

Examples of the additive agents include antifoaming agents such assilicone-based antifoaming agents and acrylic ester-based antifoamingagents; heat stabilizers; antistatic agents; ultraviolet absorbingagents; coloring agents such as dyes and pigments; lubricants; anddispersing agents such as wetting and dispersing agents. These additiveagents may be used alone or in combination.

The thermosetting resin composition is prepared through blending thethermosetting resin, curing accelerator, and any other component asrequired. Specifically, the thermosetting resin composition is preparedas follows, for example.

First, components such as the benzoxazine compound that can be dissolvedin an organic solvent are introduced into an organic solvent anddissolved to prepare a mixture. At this time, the mixture may be heatedas required. Thereafter, components that are used as required and notdissolved in the organic solvent, such as the inorganic filler, areadded to the mixture, and then the components that are not dissolved inthe organic solvent are dispersed in the mixture using a ball mill, beadmill, roll mill, or the like until they are in a predetermineddispersion state, as a result of which the thermosetting resincomposition is prepared. There is no particular limitation on theorganic solvent used here as long as it can dissolve the benzoxazinecompound and the like and does not inhibit the curing reaction. Specificexamples of the organic solvents include methyl ethyl ketone, acetone,toluene, N,N-dimethylformamide, propylene glycol monomethyl etheracetate, 1-methoxy-2-propanol, and THF.

In order to cure a thermosetting resin composition according to thisembodiment, the thermosetting resin composition can be heated to equalto or greater than a temperature at which the curing reaction of thebenzoxazine compound is substantially started. For example, it issufficient that the thermosetting resin composition be heated at atemperature of 50° C. or more to be cured, and the thermosetting resincomposition is preferably heated at a temperature within a range of 130°C. to 250° C. to be cured. Note that there is no particular limitationon a specific temperature condition under which the thermosetting resincomposition is cured, and the temperature condition can be appropriatelyset in accordance with applications of use or purposes of thethermosetting resin composition.

Although the degree of progress in the curing reaction of thethermosetting resin composition according to the present embodiment canbe measured by various methods, it can be measured through measuring agel time, as a simple method. The above-described thermosetting resin,curing accelerator, and any other components as required are blended toprepare a thermosetting resin composition, the thermosetting resincomposition is placed on a heating platen heated to a predeterminedtemperature, and then the gel time is measured while the thermosettingresin composition is being stirred on the heating platen. A time periodis measured from when the thermosetting resin composition is placed onthe heating platen to when the thermosetting resin composition isgelated (solidified) after undergoing a molten state on the heatingplaten, and then the measured time period is referred to as the “geltime”. Specifically, the gel time is preferably measured conforming to ameasurement method defined by JIS C 6521. Even though the thermosettingresin composition according to the present embodiment contains thebenzoxazine compound having a relatively slow cure rate, thethermosetting resin composition also contains the curing acceleratorcontaining the triazine thiol compound, and thus the cure rate of thebenzoxazine compound is increased. Thus, it is possible to obtain apreferred gel time for the case where the thermosetting resincomposition is hot molded for applications in various fields. Forexample, it is possible to design blending of the components of thethermosetting resin composition such that the gel time of thethermosetting resin composition at 200° C. is 7 minutes or less, andpreferably not less than 10 seconds and not more than 5 minutes.Therefore, the thermosetting resin composition is particularly usefulfor applications involving hot molding of a resin material, which willbe described later.

Next, applications of use to which the thermosetting resin compositionis applicable will be described below. There is no particular limitationon the applications of use of the thermosetting resin composition aslong as the properties of the thermosetting resin composition can beutilized, and the thermosetting resin composition is particularly usefulfor being applied to electronic materials, for example. Specifically,the thermosetting resin composition can be used as insulating materialsfor metal-clad laminates or printed-wiring boards, sealing materialsused for sealing electronic components such as semiconductor components,other molding materials in the applications that require insulationproperties or high heat resistance, and the like.

If the thermosetting resin composition is used as an insulating materialfor metal-clad laminates or printed-wiring boards, the thermosettingresin composition can be applied as a form of; a prepreg in which afiber base material is impregnated with the composition; a resin sheetin which the composition is applied onto a carrier sheet such as a metalfoil or a resin film; and the like. In other words, the prepreg can beobtained through impregnating the fiber base material with thethermosetting resin composition. Also, the resin sheet can also beobtained through applying the thermosetting resin composition onto thecarrier sheet such as a metal foil or a resin film.

A method of manufacturing a prepreg using the thermosetting resincomposition will be described below. The prepreg can be manufacturedthrough impregnating a fiber base material such as glass cloth with thethermosetting resin composition, and drying the impregnatedthermosetting resin composition to be semi-cured. At that time, in orderto impregnate the fiber base material with the thermosetting resincomposition, the thermosetting resin composition is prepared as a resinvarnish containing an organic solvent, for example. In other words,components of the thermosetting resin composition are mixed in theorganic solvent, and the thermosetting resin composition is dissolvedand dispersed therein to prepare a resin varnish in a liquid state.There is no particular limitation on the organic solvent used here aslong as it dissolves resin components such as the benzoxazine compoundand does not inhibit the curing reaction. Specific examples of theorganic solvent include methyl ethyl ketone, acetone, toluene,N,N-dimethylformamide, and propylene glycol monomethyl ether acetate.

The fiber base material such as glass cloth is impregnated with theresin varnish obtained in this manner, the impregnated fiber basematerial is heated and dried, and then the solvent is removed byvolatilization and the thermosetting resin composition is semi-cured, asa result of which a prepreg can be obtained. Examples of the fiber basematerial include glass cloth, polyester cloth, glass nonwoven fabric,aramid nonwoven fabric, pulp paper, and the like. Also, the fiber basematerial is impregnated with the resin varnish using an immersionmethod, an application method, or the like. This impregnation may berepeated several times as required. The fiber base material impregnatedwith the resin varnish may be heated and dried under a desired heatingcondition, for example, at 80 to 170° C. for 1 to 10 minutes, such thatthe curing reaction of the thermosetting resin composition has notexcessively progressed.

A method of producing a metal-clad laminate using the prepreg obtainedin this manner will be described. A metal foil is placed on both ofupper and lower sides, or any one of the upper and lower sides of theprepreg. One prepreg may be placed thereon, and alternatively aplurality of prepregs may be laminated. These are hot-press molded toproduce an integrated laminate. Accordingly, a metal-clad laminate(double-sided metal-clad laminate or one-side metal-clad laminate) canbe obtained. Examples of the metal foil include copper foil, silverfoil, aluminum foil, stainless steel foil, and the like. There is noparticular limitation on hot-press conditions, and the hot-pressconditions may be appropriately set in accordance with the thickness ofa metal-clad laminate to be manufactured, content of components of theresin composition of a prepreg, and the like, and a general exemplarycondition may be set at a temperature of 150 to 250° C., a pressure of1.5 to 4.0 MPa, a time of 60 to 150 minutes.

A treatment such as etching is performed on the metal-clad laminateobtained as described above to partially remove a metal layer (metalfoil) from the surface thereof, and thus a desired patterned circuit isformed, as a result of which a printed-wiring board including aninsulating layer and the circuit placed on the surface thereof can beobtained.

Also, this printed-wiring board is used as a base substrate, and asecond prepreg and a second metal foil are further laminated on thesurface of the base substrate and the laminated printed-wiring board ishot-press molded, as a result of which a multilayer printed-wiring boardcan also be obtained.

Next, a method of manufacturing a resin sheet using the thermosettingresin composition will be described below. For example, the resin sheetcan be obtained through applying the thermosetting resin compositiononto a carrier sheet such as a metal foil or a resin film. Thisthermosetting resin composition is prepared as a resin varnish,similarly to the above-described case where the prepreg is manufactured,for example. There is no particular limitation on the method of applyingthe thermosetting resin composition thereon, and examples of the methodinclude various types of known methods such as spin coating, dipcoating, flow coating, spray coating, roll coating, and bar coatermethods. The thermosetting resin composition is applied to form acoating film, and then the coating film is heated and dried, as a resultof which a resin sheet made of the thermosetting resin composition canbe obtained.

A method of producing a printed-wiring board using the resin sheetobtained in this manner will be described below. A base substrateincluding an insulating layer and metal layers or circuits placed onboth sides of the insulating layer is prepared. The resin sheetsupported by the carrier sheet is placed on each of both sides of thebase substrate, and then the resin sheet is heated to be cured, as aresult of which a second insulating layer made of a cured material ofthe thermosetting resin composition is formed on each of both sides ofthe base substrate. At this time, similarly to the above-described casewhere the metal-clad laminate is produced, a heating temperature iswithin a range of 80 to 170° C., for example. Furthermore, a secondcircuit is formed on the surface of the second insulating layer formedon the base substrate. If the carrier sheet is a metal foil such ascopper foil, the second circuit can be formed through performing etchingor the like on the metal foil. Also, if the carrier sheet is a resinfilm such as PET, this resin film is peeled from the second insulatinglayer, and then a plating treatment or the like is performed on theexposed second insulating layer, as a result of which the second circuitcan be formed. A multilayer can be formed through repeating theformation of the second insulating layer and the formation of the secondcircuit as required. In this manner, a multilayer printed-wiring boardcan be produced.

Next, a method of manufacturing a sealing material made of thethermosetting resin composition will be described. The sealing materialis produced as follows, for example.

First, components for the thermosetting resin composition are blended,and these components are evenly mixed using a mixer or the like toprepare a mixture. Thereafter, the mixture is further melted, mixed, andkneaded using a heat roll, kneader, or the like to obtain the sealingmaterial. The sealing material may be hot molded under a hightemperature condition. Examples of a hot molding method include lowpressure transfer molding and injection molding. Electronic componentssuch as semiconductor elements mounted on a substrate are sealed withthis sealing material, for example.

As described above, the thermosetting resin composition according to thepresent embodiment contains a curing accelerator containing a triazinethiol compound, and thereby the cure rate of the benzoxazine compoundcan be increased. Thus, it is possible to shorten a curing time for thecase where the prepreg, resin sheet, and sealing material obtained usingthe thermosetting resin composition are each hot molded to be cured, andthe thermosetting resin composition increases the productivity in thecase where a metal-clad laminate, a printed-wiring board, or the like ismanufactured using them.

Also, although the thermosetting resin composition according to thepresent embodiment contains the benzoxazine compound as a thermosettingresin, it is possible to resolve undercuring of the benzoxazine compoundin a cured material of the thermosetting resin composition. Accordingly,the thermosetting resin composition can be provided as an insulatingmaterial that can suitably exhibit excellent properties of the curedmaterial of the benzoxazine compound (for example, electrical insulatingproperties, heat resistance, and flame-retardancy). Thus, a prepreg, ametal-clad laminate in which this prepreg is used, a resin sheet, aprinted-wiring board, and a sealing material that are obtained using thethermosetting resin composition have excellent electrical insulatingproperties, heat resistance, and flame-retardancy.

EXAMPLE

Hereinafter, the present invention will be specifically described usingExamples. Note that the present invention is not limited to the Examplesdescribed below.

Examples 1 to 8 and Comparative Examples 1 to 11 Preparation ofThermosetting Resin Composition

Each component used when a thermosetting resin composition is preparedin this example will be described.

(Benzoxazine Compound)

Bisphenol F-based benzoxazine compound: compound represented by Formula(1) above (available from Shikoku Chemicals Corporation)

(Thermosetting Compound Other than Benzoxazine Compound)

Epoxy resin: HP-9500 available from DIC Corporation (epoxy equivalent:272 g/eq)

Phenol resin: TD-2090 available from DIC Corporation

Phosphorus-containing phenol resin: XZ-92741 available from The DowChemical Company

(Triazine Thiol Compound)

2,4,6-trimercapto-s-triazine: compound represented by Formula (2) above(Zisnet F available from Sankyo Kasei Co., Ltd., molecular weight: 177)

(Thiol Compound)

Thiol compound 1: 3-mercaptopropyltrimethoxysilane (available fromSankyo Kasei Co., Ltd.)

Thiol compound 2: pentaerythritol tetrakis(3-mercaptobutyrate) (KarenzMT PE1 available from Showa Denko K.K.)

Thiol compound 3: trimethylolpropane tris(3-mercaptobutyrate) (TPMBavailable from Showa Denko K.K.)

(Curing Accelerator Other than Triazine Thiol Compound)

Imidazole: 2-ethyl-4-methyimidazole (available from Shikoku ChemicalsCorporation)

[Preparation Method]

First, the aforementioned components were added at a blend ratio shownin Tables 1 and 2 to a liquid mixture of 1-methoxy-2-propanol and THF sothat the concentration of solid content was 20% by mass, and thereby themixture was obtained. The mixture obtained in this manner was stirred atroom temperature for 10 minutes to obtain a thermosetting resincomposition.

[Evaluation]

(Measurement of Gel Time of Thermosetting Resin Composition)

The gel time of the thermosetting resin composition obtained in eachExample and Comparative Example was measured at 170° C. and 200° C.,conforming to JIS C 6521.

The results of evaluation tests are shown in Tables 1 and 2.

TABLE 1 Example 1 2 3 4 5 6 7 8 Composition bisphenol F-based 10 10 1010 10 10 10 10 (parts by mass) benzoxazine compound epoxy resin  5  5phenol resin phosphorus-containing phenol resin triazine thiol  1  1 0.5  0.5  0.1  0.1  1  1 compound thiol compound 1 thiol compound 2thiol compound 3 imidazole  0.1  0.1  0.1  0.1 Evaluation gel time 42sec 50 sec  2 min  2 min  5 min  6 min 10 sec 30 sec (heated at 200° C.) 2 sec 35 sec 45 sec 50 sec gel time  2 min  7 min 17 sec  1 min (heatedat 170° C.) 40 sec  2 sec 10 sec

TABLE 2 Comparative Example 1 2 3 4 5 6 7 8 9 10 11 Compositionbisphenol F-based 10 10 10 10 10 10 10 10 10  1 (parts by benzoxazinemass) compound epoxy resin phenol resin  1  1 phosphorus-  1  2  2containing phenol resin triazine thiol  1 compound thiol compound 1  1thiol compound 2  1 thiol compound 3  1 imidazole  0.1  0.1  0.1Evaluation gel time  2 min  4 min  9 min  8 min  7 min 11 min 8 min 8min  8 min 20 min 20 min (heated at 46 sec 22 sec 28 sec 24 sec 50 sec30 sec 2 sec 35 sec or more or more 200° C.) gel time (heated at 170°C.)

As shown in Tables 1 and 2, in the case where 0.5 to 1 part by mass ofthe triazine thiol compound was blended (Examples 1 to 4), the gel timein the case where the thermosetting resin composition was heated at 200°C. was shorter than that in Comparative Examples 1 to 4 in which thetriazine thiol compound was not blended and a phenol resin or aphosphorus-containing phenol resin was blended. Also, it can beunderstood also from a comparison between Example 5 and ComparativeExample 5 or a comparison between Example 6 and Comparative Example 6that in order to accelerate curing reaction of the benzoxazine compound,it is preferable that the triazine thiol compound be blended.

On the other hand, in the case where a thiol compound that does not havea triazine ring was blended (Comparative Examples 7 to 9), there was atendency for the gel time to be longer compared to Examples 2 and 4 inwhich 0.5 to 1 part by mass of the triazine thiol compound was blended.Also, the gel time was long in the case where only the bisphenol F-basedbenzoxazine compound was blended (Comparative Example 10), and the casewhere only the triazine thiol compound was blended (Comparative Example11), compared to Examples.

Also, it can be understood from a comparison between Example 1 andExample 7 or a comparison between Example 2 and Example 8 that if thebenzoxazine compound and an epoxy resin are used in combination, a morepreferable curing acceleration effect can be obtained.

Based on the results above, it can be understood that if the curingaccelerator containing the triazine thiol compound is used for thethermosetting resin containing the benzoxazine compound, an excellentcuring acceleration effect can be obtained. Moreover, according to theseresults, it is conceivable that the present invention is widelyapplicable to various cases in which the thermosetting resin compositioncontaining the benzoxazine compound is used.

Note that although the aforementioned Examples describe cases in whichthe bisphenol F-based benzoxazine compound, which is an Fa-basedbenzoxazine compound, is used as the benzoxazine compound, the presentinvention is not limited to this. For example, a Pd-based benzoxazinecompound may be used as the benzoxazine compound.

1. A method of curing a thermosetting resin composition, comprising:mixing a thermosetting resin containing a benzoxazine compound and acuring accelerator containing a triazine thiol compound to prepare athermosetting resin composition; and heating the thermosetting resincomposition to be cured.
 2. The method of curing the thermosetting resincomposition according to claim 1, wherein the thermosetting resincomposition is heated to 50° C. or more to be cured.
 3. The method ofcuring the thermosetting resin composition according to claim 1, whereinthe triazine thiol compound includes a compound having three or morethiol groups in one molecule.
 4. The method of curing the thermosettingresin composition according to claim 1, wherein the triazine thiolcompound includes a compound having a triazine ring and a thiol groupdirectly bound to the triazine ring.
 5. The method of curing thethermosetting resin composition according claim 1, wherein a percentageof the triazine thiol compound to an entirety of the thermosetting resincomposition is within a range of 0.1 to 30% by mass.
 6. The method ofcuring the thermosetting resin composition according to claim 1, whereinthe curing accelerator further includes imidazole.
 7. The method ofcuring the thermosetting resin composition according to claim 1, whereinthe thermosetting resin further includes an epoxy resin.
 8. Athermosetting resin composition comprising a thermosetting resincontaining a benzoxazine compound and a curing accelerator containing atriazine thiol compound.
 9. The thermosetting resin compositionaccording to claim 8, wherein a gel time of the thermosetting resincomposition at 200° C. is 7 minutes or less.
 10. The thermosetting resincomposition according to claim 8, wherein the triazine thiol compoundincludes a compound having three or more thiol groups in one molecule.11. The thermosetting resin composition according to claim 8, whereinthe triazine thiol compound includes a compound having a triazine ringand a thiol group directly bound to the triazine ring.
 12. Thethermosetting resin composition according to claim 8, wherein apercentage of the triazine thiol compound to an entirety of thethermosetting resin composition is within a range of 0.1 to 30% by mass.13. The thermosetting resin composition according to claim 8, whereinthe curing accelerator further includes imidazole.
 14. The thermosettingresin composition according to claim 8, wherein the thermosetting resinfurther includes an epoxy resin.
 15. A prepreg obtained throughimpregnating a fiber base material with the thermosetting resincomposition according to claim 8, and semi-curing the thermosettingresin composition.
 16. A metal-clad laminate obtained through laminatingthe prepreg according to claim 15 with a metal foil, and hot-pressmolding the laminated prepreg.
 17. A resin sheet obtained throughapplying the thermosetting resin composition according to claim 8 onto acarrier sheet.
 18. A printed-wiring board comprising an insulating layermade of a cured material of the thermosetting resin compositionaccording to claim
 8. 19. A sealing material made of the thermosettingresin composition according to claim 8.